How Much Water Should You Drink a Day? (2026)
The “eight glasses a day” rule ignores the two things that actually move your water needs: your body size and how much you sweat. The Water Intake Calculator estimates a daily target from your weight and exercise time, shown in litres, millilitres, cups, and ounces. Here’s how daily water needs are worked out and what nudges them up or down.
How Daily Water Needs Work
Your body loses water through breathing, sweating, digestion, and exercise. A common guideline is about 30–35 ml of water per kilogram of body weight, plus extra for physical activity. The calculator personalizes this to your size and activity level.
Our Water Intake Calculator adds roughly an extra cup of water for every 30 minutes of exercise.
How to Use Our Water Intake Calculator
- Open the Water Intake Calculator.
- Choose your units and enter your body weight.
- Enter how many minutes you exercise per day.
- Read your recommended daily water in liters, ml, cups, and ounces.
- Copy or download your hydration target.
Example Targets
| Weight | Exercise | Daily Water |
|---|---|---|
| 70 kg | 0 min | ~2.3 L / 9.5 cups |
| 80 kg | 30 min | ~2.9 L / 12 cups |
| 160 lb | 60 min | ~3.2 L / 13.5 cups |
Common Use Cases
- Daily hydration — set a simple water goal.
- Fitness plans — adjust intake for training days.
- Workplace wellness — keep a bottle goal in mind.
- Health tracking — compare your actual intake to a target.
FAQ
How much water should I drink a day?
It depends on your weight and activity. A common guideline is 30–35 ml per kilogram of body weight, plus more for exercise.
Does exercise change water needs?
Yes. Sweating increases water loss, so active days require more fluids.
Do other drinks and food count?
Yes. Tea, coffee, milk, and water-rich foods all contribute to hydration.
Can I drink too much water?
Rarely, but yes. Drinking a very large amount in a short time can dilute blood sodium (hyponatremia). The calculator gives a daily target to spread across the day, not a volume to down at once — and thirst plus pale-yellow urine remain good everyday guides.
What related tools help?
For calorie and nutrition planning, use our Calorie Calculator and Macro Calculator.
Want a hydration goal that fits your body, not a generic eight glasses? The Water Intake Calculator sets one from your weight and activity — pair it with the Calorie Calculator if you’re planning meals around training.